There are known the ultra-short pulse generation method and device, which operation are based on the longitudinal laser mode-locking, where the mode-locking is achieved by using a saturable absorber, which is made from the tapered segment of an optical fiber, around which a mixture of relevant polymer and carbon nanotubes is wrapped. Light, propagating through the tapered segment of the optical fiber, penetrates outside and interacts with the carbon nanotubes. Saturable absorption and mode-locking are possible due to the unique characteristics of carbon nanotubes. Known method and device are described in the United States patent application US2011/0280263A1, 2011.
The disadvantage of this method and device is that the saturable absorbers based on the carbon nanotubes and polymer mixture, similarly to the saturable semiconductor absorbers (SESAM), tend to degrade. A lifetime of the oscillator is strongly limited due to this adverse feature. In addition, using this method, sometimes is not possible to achieve mode-locking due to the improper spectral, temporal and energetic characteristic of the carbon nanotubes.
There are known the ultra-short pulse generation method and device, which operation are based on the longitudinal laser mode-locking, where the mode locking is achieved by the nonlinear polarization rotation effect due to the optical Kerr effect inside an optical fiber, where pulse formation inside the resonator with a normal dispersion is achieved by spectral filtering of the spectrally broadened pulse caused by self-phase modulation due to the optical Kerr effect inside the optically transparent material. Strongly chirped picosecond pulses are created inside the resonator of the oscillator because of spectral filtering, and laser pulses can be compressed up to femtosecond durations at the output of the oscillator. The known method and device are described in the United States patent application US2010220751A1, 2010.
The disadvantage of this known method and device is that it is very unstable to any external disturbances, sensitive to the ambient temperature fluctuations and is suitable for use only under laboratory conditions. Even in this way, the parameters of the generated pulses are often unpredictable because the mode locking is achieved using non-polarization maintaining optical fibers.